121 research outputs found
Deriving Iodine-free spectra for high-resolution echelle spectrographs
We describe a new method to derive clean, iodine-free spectra directly from
observations acquired using high-resolution echelle spectrographs equipped with
iodine cells. The main motivation to obtain iodine-free spectra is to use
portions of the spectrum that are superimposed with the dense forest of iodine
absorption lines, in order to retrieve lines that can be used to monitor the
magnetic activity of the star, helping to validate candidate planets. In short,
we provide a straight-forward methodology to clean the spectra by using the
forward model used to derive radial velocities, the Line Spread Function
information plus the stellar spectrum without iodine to reconstruct and
subtract the iodine spectrum from the observations. We show our results using
observations of the star Ceti acquired with the PFS, HIRES and UCLES
spectrographs, reaching an iodine-free spectrum correction at the 1% RMS
level. We additionally discuss the limitations and further applications of the
method.Comment: 15 pages, 7 figures. Accepted for publication in A
Search for nearby Earth analogs I. 15 planet candidates found in PFS data
30 pages, 20 figures, 3 tables, accepted for publication in ApJSThe radial velocity (RV) method plays a major role in the discovery of nearby exoplanets. To efficiently find planet candidates from the data obtained in high-precision RV surveys, we apply a signal diagnostic framework to detect RV signals that are statistically significant, consistent in time, robust in the choice of noise models, and do not correlated with stellar activity. Based on the application of this approach to the survey data of the Planet Finder Spectrograph, we report 15 planet candidates located in 14 stellar systems. We find that the orbits of the planet candidates around HD 210193, 103949, 8326, and 71135 are consistent with temperate zones around these stars (where liquid water could exist on the surface). With periods of 7.76 and 15.14 days, respectively, the planet candidates around star HIP 54373 form a 1:2 resonance system. These discoveries demonstrate the feasibility of automated detection of exoplanets from large RV surveys, which may provide a complete sample of nearby Earth analogs.Peer reviewedFinal Accepted Versio
EPIC247098361b: a transiting warm Saturn on an eccentric days orbit around a star
We report the discovery of EPIC247098361b using photometric data of the
Kepler K2 satellite coupled with ground-based spectroscopic observations.
EPIC247098361b has a mass of M M, a radius of
R R, and a moderately low equilibrium temperature of
K due to its relatively large star-planet separation of
AU. EPIC247098361b orbits its bright () late F-type host star
in an eccentric orbit () every 11.2 days, and is one of only
four well characterized warm Jupiters having hosts stars brighter than .
We estimate a heavy element content of 20 7 M for
EPIC247098361b, which is consistent with standard models of giant planet
formation. The bright host star of EPIC247098361b makes this system a well
suited target for detailed follow-up observations that will aid in the study of
the atmospheres and orbital evolution of giant planets at moderate separations
from their host stars.Comment: 11 pages, 10 figures, submitted to MNRA
3-Phase 4-wire matrix converter-based voltage sag/ swell generator to test low-voltage ride through in wind energy conversion systems
The high penetration of energy from wind energy conversion systems (WECSs) can have a significant influence on the stability, power quality and reliability of power systems. Therefore several countries have developed stringent grid codes in recent years in order to enhance the overall stability of power systems. In these grid codes, the capacity to fulfil low-voltage ride through (LVRT) requirements is considered an important issue for the control of WECSs. Therefore in this study, a novel voltage sag/ swell generator (VSG) based on a 4-leg matrix converter is presented. This VSG can be used to generate the symmetrical and asymmetrical faults required to test LVRT algorithms in a laboratory environment. The performance of the VSG is experimentally demonstrated and compared with the operation of other VSGs conventionally used for LVRT studies
Application of the DNA-Specific stain methyl green in the fluorescent labeling of embryos
Methyl green has long been known as a histological stain with a specific affinity for DNA, although its fluorescent properties have remained unexplored until recently. In this article, we illustrate the method for preparing a methyl green aqueous stock solution, that when diluted can be used as a very convenient fluorescent nuclear label for fixed cells and tissues. Easy procedures to label whole zebrafish and chick embryos are detailed, and examples of images obtained shown. Methyl green is maximally excited by red light, at 633 nm, and emits with a relatively sharp spectrum that peaks at 677 nm. It is very inexpensive, non-toxic, highly stable in solution and very resistant to photobleaching when bound to DNA. Its red emission allows for unaltered high resolution scanning confocal imaging of nuclei in thick specimens. Finally, this methyl green staining protocol is compatible with other cell staining procedures, such as antibody labeling, or actin filaments labeling with fluorophoreconjugated phalloidi
The test case of HD26965: difficulties disentangling weak Doppler signals from stellar activity
We report the discovery of a radial velocity signal that can be interpreted
as a planetary-mass candidate orbiting the K dwarf HD26965, with an orbital
period of 42.3640.015 days, or alternatively, as the presence of residual,
uncorrected rotational activity in the data. Observations include data from
HIRES, PFS, CHIRON, and HARPS, where 1,111 measurements were made over 16
years. Our best solution for HD26965 is consistent with a super-Earth that
has a minimum mass of 6.920.79 M orbiting at a distance of
0.2150.008 AU from its host star. We have analyzed the correlation between
spectral activity indicators and the radial velocities from each instrument,
showing moderate correlations that we include in our model. From this analysis,
we recover a 38 day signal, which matches some literature values of the
stellar rotation period. However, from independent Mt. Wilson HK data for this
star, we find evidence for a significant 42 day signal after subtraction of
longer period magnetic cycles, casting doubt on the planetary hypothesis for
this period. Although our statistical model strongly suggests that the 42-day
signal is Doppler in origin, we conclude that the residual effects of stellar
rotation are difficult to fully model and remove from this dataset,
highlighting the difficulties to disentangle small planetary signals and
photospheric noise, particularly when the orbital periods are close to the
rotation period of the star. This study serves as an excellent test case for
future works that aim to detect small planets orbiting `Sun-like' stars using
radial velocity measurements.Comment: 16 pages, 10 figures, 13 tables, accepted for publication in A
Probiotic activity of <i>Enterococcus faecalis</i> CECT7121: effects on mucosal immunity and intestinal epithelial cells
Aims: To analyse the effect of Enterococcus faecalis CECT7121 on intestinalepithelial cells (IECs) and its effects on the mucosal immune response.
Methods and Results: Enterococcus faecalis CECT7121 showed a high adhesioncapacity to completely and heterogeneously differentiated human intestinalepithelial cell line (Caco-2 cells). In addition, the contact of this bacteriumwith Caco-2 cells did not induce inflammatory chemokines (IL-8 and CCL-20). The presence of IgA⁺ and IL-6⁺ cells in the small intestine, as well as theproduction of inflammatory cytokines (TNFa, IL-6 and IL-12) in the gut, wasdetermined after intragastric inoculation of Ent. faecalis CECT7121 in BALB/cmice. The administration of Ent. faecalis CECT7121 increased the number ofIgA⁺ cells in the intestinal lamina propria without modifying the percentage ofIL-6⁺ cells. No differences were observed in the cytokines measured in theintestinal extracts between probiotic-treated and control mice.
Conclusions: Enterococcus faecalis CECT7121 stimulates local mucosalimmunity and adheres to IECs without inducing inflammatory signals.
Significance and Impact of the Study: Our results indicate that, apart from itsalready reported systemic immune activity, Ent. faecalis CECT7121 has amodulatory effect at a local level.Centro Universitario de Estudios Microbiológicos y Parasitológico
TOI-150: A transiting hot Jupiter in the TESS southern CVZ
We report the detection of a hot Jupiter ($M_{p}=1.75_{-0.17}^{+0.14}\
M_{J}R_{p}=1.38\pm0.04\ R_{J}\log
g=4.152^{+0.030}_{-0.043}\beta=-79.59^{\circ}$). We confirm the
planetary nature of the candidate TOI-150.01 using radial velocity observations
from the APOGEE-2 South spectrograph and the Carnegie Planet Finder
Spectrograph, ground-based photometric observations from the robotic
Three-hundred MilliMeter Telescope at Las Campanas Observatory, and Gaia
distance estimates. Large-scale spectroscopic surveys, such as APOGEE/APOGEE-2,
now have sufficient radial velocity precision to directly confirm the signature
of giant exoplanets, making such data sets valuable tools in the TESS era.
Continual monitoring of TOI-150 by TESS can reveal additional planets and
subsequent observations can provide insights into planetary system
architectures involving a hot Jupiter around a star about halfway through its
main-sequence life.Comment: 13 pages, 3 figures, 2 tables, accepted to ApJ
Prevalence of HIV drug-resistance mutations in HIV-infected Mexican patients heavily experienced to antiretroviral therapy
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